Cleaning or descaling operations with a high-pressure liquid-jet are being used ever more widely. The machines operate with extremely high pressure, occasionally in the neighborhood of 1000 bar. A liquid ejected from a liquid-jet gun at such a pressure carries considerable energy and is extremely useful in many cleaning operations, as well as in steel mill descaling operations and even some mining operations.
The use of such extremely high pressure does pose an increased danger to the users of such a liquid-jet gun. Such a gun is normally provided with an elongated pistol-type housing having a pistol grip associated with a large trigger that operates a valve inside the housing. When this trigger is drawn back the valve is opened and the high-pressure liquid jet issues from the tip of the barrel of such a gun. In order to prevent accidental actuation of this trigger, a safety is provided, normally in the form of a laterally displaceable button carried on the housing adjacent the trigger and depressable to prevent drawing-back of the trigger. Thus this safety can be engaged when the gun is not in use to prevent accidental actuation of the trigger.
Such an arrangement has considerable disadvantages. First of all a hurried or careless worker will frequently forget to actuate the safety when the gun is not to be used. Secondly the gun is often itself yanked to pull the high-pressure hose connected to it along as the cleaning operation or the like progresses. In order to gain a good grip the user frequently also grips the trigger, which should during such an operation be held in its advanced position by the safety. As a considerable pull is frequently exerted to move the tubing of such a gun along, the safety mechanism is often excessively loaded and at times broken by the user.